PROJECT SUMMARY Acute Myeloid Leukemia (AML) is a heterogeneous disease characterized by an accumulation of rapidly proliferating neoplastic cells of the myeloid lineage with differentiation defects. The hallmarks of leukemic cells in AML include increased cell survival, as well as altered cellular metabolism and mitochondrial functionality. In spite of the vast amount of information known about AML and the identification of favorable prognosis factors, a very large proportion of patients relapse and die from their disease. The inter- and intra-tumor heterogeneity of AML makes the identification of therapeutic targets for this disease particularly challenging. Therefore, there is an urgent need to identify multi-targeted agents that could target AML as a composite disease. Nicotinamide phosphoribosyltransferase (NAMPT) is a protein involved in the generation of NAD+ in tumor cells. Leukemic blasts show a higher NAD+ turnover rate than normal cells, suggesting that NAD+ biosynthesis could be critically required in hematologic malignancies and therefore targeting the regeneration of NAD+ offers an attractive alternative strategy in AML. Unlike many targeted therapies that can only be directed at one genetic/molecular subtype of AML, targeting regeneration of NAD+ via NAMPT inhibition could be relevant to a much broader group based upon the metabolic differences between tumor and normal cells. While two agents targeting NAMPT have been tested in Phase I clinical trials, dose-limiting toxicities including thrombocytopenia and gastrointestinal toxicities led to their clinical discontinuation. Novel compounds with improved tolerability are needed. Our studies utilize a novel NAMPT inhibitor, KPT-9274, developed by Karyopharm Therapeutics for which our data demonstrate potent cytotoxic effects in AML cell lines and primary AML blasts in vitro and in vivo. Preliminary toxicology data shows acceptable properties of KPT-9274, which differentiate it from other previously examined NAMPT inhibitors. KPT-9274 is currently being examined in a phase 1 study for solid tumor patients. Our preliminary data demonstrates that inhibition of NAMPT using KPT-9274, leads to increased apoptosis and decreased proliferation of AML cell lines and primary AML cells with minimal toxicity in normal hematopoietic cells. KPT-9274 was also able to prolong the time to disease progression in vivo and improve overall survival in an AML cell line-disseminated xenograft mouse model. With this proposal we aim to 1) to determine how NAMPT affects metabolism and self-renewal in AML immature myeloid cells and their normal counterparts while examining for distinct subtypes of AML that might be exquisitely sensitive to this class of drugs; 2) test rational combination therapies as well as identify novel synthetic lethal partners with NAMPT inhibitors; and 3) to initiate a Phase Ib/II trial with KPT-9274 as single agent priming followed by combination with decitabine that includes detailed pharmacodynamic assessment in patients with relapsed and refractory AML. At completion of this project it is anticipated that the approaches brought forward will lead to new treatment strategies involving NAMPT inhibition with KPT-9274 in patients with AML.